<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>5.border-radius</title>
  <style>
    * {margin: 0; padding: 0;}
    .father {
      width: 200px;
      height: 200px;
      border: 50px solid #000;
      margin: 0 auto;

      /* 当border-radius的值大于border的值时，外边框和内容区域都有圆角*/
      /* border-radius: 60px; */

      /* 当border-radius的值小于border的值时，外边框有圆角，内容区域无圆角*/
      border-radius: 40px;
    }
    
    .tuoyuan {
      width: 400px;
      height: 200px;
      border: 1px solid #000;
      box-sizing: border-box;
      margin: 0 auto;

      border-radius:  50%;

      /* border-top-left-radius: 200px 100px;
      border-top-right-radius: 200px 100px;
      border-bottom-right-radius: 200px 100px;
      border-bottom-left-radius: 200px 100px; */
    }
  </style>
</head>
<body>
  <div class="father"></div>

  <!-- 画椭圆 -->
  <div class="tuoyuan">

  </div>
</body>
</html>